DESCRIPTION: The aim of this research is to study the structure and function of three membrane enzymes and transporters. The objective is to understand the function of these membrane proteins at the molecular level and to describe the biological significance of their activity. The questions about the (NaK)ATPase are the nature of the interactions between the alpha and beta chains, and the regulation of the alpha2 isoform of the pump. The structure and function of the ectoapyrases, membrane-bound enzymes present on all animal and many higher eukaryotic cells, will be explored through isolation of the gene, identification of inhibitors of the activity, and modification of the activity. The plan to isolate the enzyme from plant tissue and to use this form of the enzyme to identify related proteins in animal cells. The aim is to determine the physiological function of the enzyme. The identification, isolation, and characterization of non-mitochondrial transport systems for ATP in animal and yeast cells will be carried out, with special interest in the mechanism of ATP movement to the extracellular milieu. The question of interest is the structure of the transporters that effect net transport of the nucleotide.